Bidirectional and dynamically tunable THz absorber with Dirac semimetal.

Traditional absorbers are usually sandwich structures in which a metallic ground plane is employed to prevent the transmission. Such absorbers suffer from a major drawback that incident light can only irradiate from the front of the absorbers. In this paper, a novel absorber with bulk Dirac semimetal (BDS)-AlCuFe quasicrystals is proposed to realize bidirectional and dynamically tunable terahertz (THz) perfect absorption. The proposed structure consists of two layers of AlCuFe plates with rectangular apertures and a dielectric spacer. By adjusting transverse distance between the top and bottom rectangular apertures, perfect absorption could be realized under TM polarization. Simulation results show that perfect absorption can be obtained whether light irradiates from the front or back of the system, indicating a performance of bidirectional absorption. In addition, benefiting from the variable Fermi level of AlCuFe, the resonance frequency can be dynamically tuned in the THz range. Our work will stimulate more investigations on BDS-based bidirectional absorbers and optical modulators.